Topical administration of active ingredients advantageously allows the maximum concentration of the ingredient directly near the biophase and contemporaneously avoids that its dispersion into tissues may cause unnecessary risks of toxicity or intolerance.
Residence time of the composition at the site of application is critically affected by the consistency of the composition. Therefore, in the particular case of a pharmaceutical composition, a non-optimized vehicle can negatively affect the therapeutic efficacy of such composition.
In the case of cutaneous administration, a high viscosity of the composition requires a stronger spreading, causing burning or pain if the tissues are irritated or damaged; whereas a non-viscous composition can be fastly eliminated from the site of application.
In the particular case of topical pharmaceutical compositions, the sustained release of the active ingredient is frequently addressed. In this regard, the sustained release of an active ingredient involves polymers that typically release the drug at a controlled rate due to diffusion out of the polymer or by dilution of the polymer over time. Topical administration of drugs changes the rate at which drugs enter the tissue and the pharmacokinetics of the drug, thus the correctly designed materials can optimize the therapeutic effect by controlling the drug release rate.
Thus, there remains a long-felt and unmet need for a material which allows the appropriate deliver of the active ingredient.
In addition to the above, the skilled person further faces with other technical drawbacks when formulating a topical pharmaceutical composition, due to the nature of the active ingredient included therein. Some of the active ingredients known in the state of the art have a low solubility in water or are almost totally insoluble in hydrophobic solvent systems.
It is accordingly difficult to produce a topical formulation containing a sufficient dissolved concentration of active ingredient for it to exert its full effect and also to optimize the flux of the compound into the skin.
In addition to ease of release, it is also important that any formulation of a pharmaceutically active compound should be stable for long periods of time, should not lose its potency, should not discolor or form insoluble substances or complexes, and also should not be unduly irritating to the skin or mucosa.
In spite of the efforts made, there is still the need of providing topical compositions with appropriate bioadhesion, stability, and improved bioavailability of the active ingredients included therein.